instead of just "htmlhead" and "htmltail" there are now:
"sourcehead" and "sourcetail"
"sourcedirhead" and "sourcedirtail"
"findhead" and "findtail"
"identhead" and "identtail"
"searchhead" and "searchtail"
so that each CGI can have its own custom headers and footers.
If (for example) identhead isn't configured in lxr.conf, then
htmlhead will be used instead.
"sourcedir*" is used in preference to "source*" when the output
of the "source" script is a CGI. If sourcedir* aren't configured,
then it falls back to "source*" (and from there to "html*")
